"Stateful" refers to a system or application that maintains the state of its interactions over time. This means that it remembers previous actions or data, allowing for a more personalized and continuous experience. For example, a stateful web application can keep track of user sessions, preferences, and data inputs, making it easier for users to navigate and interact with the system. In contrast, a stateless system does not retain any information about past interactions. Each request is treated independently, which can simplify design but may require users to re-enter information. Understanding the difference between stateful and stateless systems is crucial in fields like software development and networking.